5.4. Gene Therapy
The very latest attempts to manage diabetes have focused on gene therapy. Every cell in the body carries the insulin gene, but it is only switched on in the b-cells in the islets in the pancreas. In order to produce human insulin in fermentation, genetic engineers have inserted an active insulin gene into bacteria so that they can produce it in vast quantities. In theory in should also be possible to implant a cell line in to the body which also produces insulin. It would have to be encapsulated to protect it from the immune system of the body, and it should also function in a similar way to islet cells, that is only produce insulin when blood sugar levels are high. Several interesting cells lines are being investigated. Some have been engineered and others have been found naturally in tumors. Table 5.4.1. lists some of the most actively investigated lines, with some of their characteristics. AtT-20 has been encapsulated in alginate. There is great hope that one day in the not too distant future, diabetes will be managed not by daily insulin injections, but with a single implantation of a set of cells that will secrete insulin in the same way as normal islet cells, and that diabetics will not longer be troubled by the many side effects that come when blood glucose levels fluctuate widely about the norm. If a cure does come, bioengineers will have played a large and vital role in its realization.
Table 5.4.1. Insulin secreting cell lines
Insulinoma cell line
Glut-2 & Glucokinase expressed, but gradually lose that
& the ability for glucose stimulated insulin release (GSIR)
|INS-1||Retains high GSIR. Cell growth slow|
|MIN-7||Expresses GLUT-1 not GLUT-2 as major glucose transporter isoform|
|MIN-6||Expresses GLUT-2, and normal GSIR|
Expresses GLUT-2 and normal GSIR, and Glucokinase:
Hexokinase activity ratio similar to normal islets
Derived from non-islet cells. Insulin secretion stimulated by
cAMP. Secretes mature insulin.